Fuel pump

ABSTRACT

A fuel pump improved in pump efficiency is provided. An impeller rotating in a pump casing has an approximately disk-shaped configuration with a group of recesses formed in a region extending along the outer peripheries of the obverse and reverse sides of the impeller. The recesses are repeatedly arranged at a distance between each other in the circumferential direction with a partition provided between each pair of adjacent recesses. The radially inner and outer end portions of the partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller. With this fuel pump, the incidence of separation or vortex formation in the flow of fuel is minimized, and a high pump efficiency can be obtained. It is preferable that the maximum amount of curvature of the partition should be from 0.1 to 1.0 mm, and the curved configuration of the rotation direction forward side of each partition on the obverse and reverse sides should be a circular arc with a radius of from 2.3 to 4.3 mm, and/or the curved configuration of the rotation direction rearward side of each partition should be a circular arc with a radius of from 3.0 to 5.0 mm.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a fuel pump adapted to suck in and pressurize a fuel such as gasoline and discharge the pressurized fuel.

[0003] 2. Discussion of Related Art

[0004] There is known a fuel pump adapted to suck in and discharge a fuel by rotating an impeller in a pump casing. An example of this type of fuel pump is disclosed in Published Japanese Translation of PCT International Publication No. Hei 9-511812. The impeller rotating in the pump casing has an approximately disk-shaped configuration. A group of recesses are formed in a region extending along the outer peripheries of the obverse and reverse sides of the disk-shaped impeller. The recesses are repeatedly arranged at a distance between each other in the circumferential direction with a partition provided between each pair of adjacent recesses. The impeller is rotated at high speed about an axis of rotational symmetry by a motor.

[0005] The lifetime of fuel pumps is mostly determined by the progression of wear between the commutator and brush of the motor. The wear progression rate is closely related to the motor current value. That is, the smaller the motor current, the lower the wear progression rate. For this reason, there is a demand that the lifetime of fuel pumps should be extended by increasing the pump efficiency and reducing the motor current to thereby lower the wear progression rate.

[0006] With the technique disclosed in the above-mentioned Publication No. Hei 9-511812, partitions forming a group of recesses repeatedly arranged in the circumferential direction on the obverse and reverse sides of the impeller are inclined to improve the pump efficiency. That is, the above-mentioned Publication No. Hei 9-511812 teaches a technique wherein the radially outer end portion of each partition is displaced forward in the rotation direction with respect to the radially inner end portion thereof, thereby improving the pump efficiency.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to further improve the pump efficiency.

[0008] The fuel pump created by the present invention is characterized in that an impeller rotating in a pump casing has an approximately disk-shaped configuration with a group of recesses formed in a region extending along the outer peripheries of the obverse and reverse sides of the impeller. The recesses are repeatedly arranged at a distance between each other in the circumferential direction with a partition provided between each pair of adjacent recesses. The radially inner and outer end portions of the partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller.

[0009] With this fuel pump, the incidence of separation or vortex formation in the flow of fuel is minimized, and a high pump efficiency can be obtained.

[0010] When the diameter of the impeller is from 30 to 36 mm, it is preferable that the radial length of each partition should be from 2.9 to 4.5 mm, and the circumferential distance between each pair of adjacent partitions should be from 1.5 to 2.5 mm, and further the thickness of each partition should be from 0.2 to 1.5 mm. Further, it is preferable that the thickness of the impeller should be from 3.0 to 4.5 mm, and the maximum amount of curvature of the partition should be from 0.1 to 1.0 mm. Alternatively, it is preferable that the curved configuration of the rotation direction forward side of each partition on the obverse and reverse sides should be a circular arc with a radius of from 2.3 to 4.3 mm, and/or that the curved configuration of the rotation direction rearward side of each partition on the obverse and reverse sides should be a circular arc with a radius of from 3.0 to 5.0 mm.

[0011] It is preferable that the fuel pump should have the following features (a) to (d21) in addition to the feature that the radially inner and outer end portions of each partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller:

[0012] (a) The partition is inclined rearward in the direction of rotation as the distance from the obverse and reverse sides increases inward in the direction of thickness.

[0013] (a1) The partition is inclined at from 40° to 60° from the middle plane in the direction of thickness.

[0014] (a2) The partition continuously extends while defining a gently arcuate surface at the rotation direction forward side of the middle plane in the direction of thickness.

[0015] (b) The thickness of the partition increases as the distance from the obverse and reverse sides increases inward in the direction of thickness.

[0016] (b1) The thickness of the partition at the middle plane in the direction of thickness is greater than the thickness at the obverse and reverse sides by from 0.1 to 0.4 mm.

[0017] (c) The radially inner end face of the recess located between each pair of adjacent partitions has two arcuate surfaces contacting each other at the middle plane in the direction of thickness.

[0018] (c1) The radius of the arcuate surfaces is from 0.7 to 2.2 mm.

[0019] (d) The radially outer end face of the recess located between each pair of partitions is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness.

[0020] (d1) The radially outer end face of the recess located between each pair of partitions is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness at an open angle of not more than 20°.

[0021] (d2) The radially outer end face of the recess has two arcuate surfaces contacting each other at the middle plane in the direction of thickness.

[0022] (d21) The radius of the arcuate surfaces is from 0.2 to 1.0 mm.

[0023] If the fuel pump has one of these features or a plurality of them in combination, the pump efficiency increases, and the pump driving current is minimized. Consequently, the pump lifetime is increased.

[0024] In the fuel pump according to the present invention, the impeller has recesses repeatedly formed in the circumferential direction at a distance between each other in a region extending along the outer peripheries of the obverse and reverse sides of the impeller, and a partition is provided between each pair of adjacent recesses. The radially inner and outer end portions of the partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller. Accordingly, the pump efficiency increases, and the pump driving current is minimized. Consequently, the pump lifetime is increased.

[0025] Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

[0026] The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a sectional view of a fuel pump according to an embodiment of the present invention.

[0028]FIG. 2 is a plan view of an impeller.

[0029]FIG. 3 is an enlarged plan view of a part of the impeller.

[0030]FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3.

[0031]FIG. 5 is a sectional view taken along the line V-V in FIG. 3.

[0032]FIG. 6 is a diagram corresponding to FIG. 5, showing a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] First, let us list useful features for improvement of the pump efficiency among those residing in embodiments of the present invention:

[0034] A. The radially inner and outer end portions of each partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller. This feature is important. The present invention utilizes this feature. In this case, it is preferable that the fuel pump should further have the following features. In particular, numerical conditions stated below should preferably be satisfied in order to obtain a high efficiency when the fuel pump is designed so that “the outer diameter of the impeller is from 30 to 36 mm; the radial length of each partition is from 2.9 to 4.5 mm; the circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; the thickness of each partition is from 0.2 to 1.5 mm; and the thickness of the impeller is from 3.0 to 4.5 mm”.

[0035] A1: The maximum amount of curvature of the partition should preferably be from 0.1 to 1.0 mm.

[0036] A2: Alternatively, the radius of curvature of the rotation direction forward side should preferably be from 2.3 to 4.3 mm.

[0037] A3: Alternatively, the radius of curvature of the rotation direction rearward side should preferably be from 3.0 to 5.0 mm.

[0038] B. The partition is inclined rearward in the direction of rotation as the distance from the obverse and reverse sides increases inward in the direction of thickness. In this case, the partition should preferably be as follows.

[0039] B1: The angle of inclination with respect to the middle plane in the direction of thickness should preferably be from 40° to 60°.

[0040] B2: In addition, the inclined partition should preferably continuously extend while defining a gently arcuate surface at the rotation direction forward side of the middle plane in the direction of thickness.

[0041] C. The thickness of the partition increases as the distance from the obverse and reverse sides increases inward in the direction of thickness.

[0042] C1: The thickness of the partition at the middle plane in the direction of thickness should preferably be greater than the thickness at the obverse and reverse sides by from 0.1 to 0.4 mm.

[0043] D. The radially inner end face of a fuel accommodating space (recess) formed between each pair of adjacent partitions has two arcuate surfaces contacting each other at the middle plane in the direction of thickness. In this case, the following is preferable:

[0044] D1: The radius of the arcuate surfaces should preferably be from 0.7 to 2.2 mm.

[0045] E. The radially outer end face of the fuel accommodating space (recess) formed between each pair of adjacent partitions is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness.

[0046] E1: The open angle of the radially outer end face of each recess should preferably be not more than 20°. Alternatively, or in addition to this feature, the following is preferable:

[0047] E2: The radially outer end face of each recess should preferably have two arcuate surfaces contacting each other at the middle plane in the direction of thickness.

[0048] E3: The radius of the arcuate surfaces should preferably be from 0.2 to 1.0 mm. With this arrangement, a high efficiency can be obtained.

[0049] A fuel pump according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The fuel pump according to this embodiment is a fuel pump for use in an automobile, which is used in a fuel tank to supply fuel to the engine of the automobile.

[0050]FIG. 1 is a sectional view of the fuel pump. In the figure, the fuel pump has a pump part 1 and a motor part 2 for driving the pump part 1. The motor part 2 comprises a brush DC motor. The motor part 2 has an approximately circular cylinder-shaped pump housing 4. A magnet 5 is disposed in the pump housing 4. A rotor 6 is disposed in the pump housing 4 in concentric relation to the magnet 5.

[0051] The rotor 6 has a shaft 7. The lower end portion of the shaft 7 is rotatably supported through a bearing 10 by a pump cover 9 secured to the lower end portion of the pump housing 4. The upper end portion of the shaft 7 is rotatably supported through a bearing 13 by a motor cover 12 secured to the upper end portion of the pump housing 4.

[0052] In the motor part 2, the rotor 6 is rotated by supplying electric power to the coil (not shown) of the rotor 6 through a terminal (not shown) provided on the motor cover 12. It should be noted that the arrangement of the motor part 2 is well known. Therefore, a detailed description thereof is omitted. It should also be noted that the motor part 2 can use a motor structure other than the illustrated one.

[0053] The arrangement of the pump part 1 driven by the motor part 2 will be described below. The pump part 1 comprises a pump cover 9, a pump body 15, and an impeller 16. The pump cover 9 and the pump body 15 are formed by die casting of aluminum, for example. When combined together, the pump cover 9 and the pump body 15 constitute a pump casing 17 for accommodating the impeller 16.

[0054] The impeller 16 is formed by molding of a resin material. As shown in FIG. 2, the impeller 16 has an approximately disk-shaped configuration. A group of recesses 16 a are formed in a region extending along the outer peripheries of the obverse and reverse sides of the disk-shaped impeller 16. The recesses 16 a are repeatedly arranged in the circumferential direction at a distance between each pair of adjacent recesses 16 a. The center of the impeller 16 is formed with an approximately D-shaped engagement hole 16 n. The engagement hole 16 n is engaged with an engagement shaft portion 7 a with a D-shaped sectional configuration at the lower end of the shaft 7. Thus, the impeller 16 is connected to the shaft 7 so as to be rotatable simultaneously with the shaft 7 and slightly movable in the axial direction. The outer peripheral surface 16 p of the impeller 16 is a circumferential surface.

[0055]FIG. 3 is an enlarged view of the impeller 16. A partition 16 b is ensured between each pair of adjacent recesses 16 a. The impeller 16 has the following features (a) to (o):

[0056] (a) The outer diameter D of the impeller is set to from 30 to 36 mm; the radial length W of each partition is set to from 2.9 to 4.5 mm; the circumferential distance L between each pair of adjacent partitions is set to from 1.5 to 2.5 mm; the thickness t of each partition is set to from 0.2 to 1.5 mm; and the thickness T of the impeller is set to from 3.0 to 4.5 mm.

[0057] (b) The radially inner end portion 16 b 1 and the radially outer end portion 16 b 2 of the partition 16 b are positioned on the same radius 16 q, and the radially middle portion 16 r of the partition 16 b is curved rearward R in the direction of rotation of the impeller.

[0058] (c) The maximum amount of curvature A of the partition 16 b is from 0.1 to 1.0 mm.

[0059] (d) The radius of curvature R3 of the rotation direction forward side is from 2.3 to 4.3 mm.

[0060] (e) The radius of curvature R4 of the rotation direction rearward side is from 3.0 to 5.0 mm.

[0061] (f) As shown in FIG. 4, the partition 16 b is inclined rearward R in the direction of rotation as the distance from the obverse and reverse sides increases inward in the direction of thickness.

[0062] (g) The angle of inclination with respect to the middle plane 16 s in the direction of thickness is from 40° to 60°.

[0063] (h) The inclined partition 16 b continuously extends while defining a gently arcuate surface 16 f at the rotation direction forward side F of the middle plane 16 s in the direction of thickness.

[0064] (i) The thickness of the partition 16 b increases as the distance from the obverse and reverse sides increases inward in the direction of thickness. In the figure, reference symbol 16 e denotes a surface that the partition 16 b would have when the front surface 16 c is not curved. Reference symbol t1 denotes the thickness of the partition 16 b at the middle plane 16 s in the direction of thickness. Reference symbol t2 denotes the thickness of the partition 16 b at the obverse and reverse sides. t1 is greater than t2. t1−t2 is from 0.1 to 0.4 mm.

[0065] (j) As shown in FIG. 5, the radially inner end face of a fuel accommodating space 16 a (recess) formed between each pair of adjacent partitions 16 b has two arcuate surfaces 16 g and 16 h contacting each other at the middle plane 16 s in the direction of thickness.

[0066] (k) The radius R1 of the arcuate surfaces 16 g and 16 h is from 0.7 to 2.2 mm.

[0067] (l) As shown in FIG. 5, the radially outer end face 16 i (16 j) of the fuel accommodating space 16 a (recess) formed between each pair of adjacent partitions 16 b is slanted to face toward the obverse and reverse sides from the middle plane 16 s in the direction of thickness.

[0068] (m) The open angle of the radially outer end face of each recess is not more than 20°. Alternatively, as shown in FIG. 6, which shows a second embodiment of the present invention, the radially outer end face 16 i (16 j) of each fuel accommodating space 16 a (recess) may be arranged as follows.

[0069] (n) The radially outer end face 16 i (16 j) has two arcuate surfaces 16 k and 16 m contacting each other at the middle plane 16 s in the direction of thickness.

[0070] (o) The radius of the arcuate surfaces 16 k and 16 m is from 0.2 to 1.0 mm.

[0071] As shown in FIG. 1, the pump cover 9 has a circumferentially extending recess 21 for forming a circumferentially extending flow passage groove between the same and the group of recesses 16 a of the impeller 16. The pump cover 9 further has a discharge opening 24 communicating with the downstream end of the recess 21. Further, the pump cover 9 has a circumferential wall 9 b. As shown in FIG. 1, the discharge opening 24 extends through the pump cover 9 to communicate with a space 2 a in the motor part 2. The inner peripheral surface 9 c of the circumferential wall 9 b faces the outer peripheral surface 16 p of the impeller 16 across a clearance.

[0072] The pump body 15 is laid on the pump cover 9. In this state, the pump body 15 is secured to the lower end portion of the pump housing 4 by caulking or the like. A thrust bearing 18 is secured to the impeller-side surface of a central portion of the pump body 15. The thrust bearing 18 bears the thrust load of the shaft 7. The pump cover 9 and the pump body 15 constitute a pump casing 17. The impeller 16 is accommodated in the pump casing 17 so as to be rotatable and slightly movable in the axial direction. The inner surface of the pump body 15 is formed with a circumferentially extending recess 20 for forming a circumferentially extending flow passage groove between the same and the group of recesses 16 a of the impeller 16. The pump body 15 further has a suction opening 22 communicating with the upstream end of the recess 20.

[0073] The circumferentially extending recess 21 of the pump cover 9 and the circumferentially extending recess 20 of the pump body 15 extend along the rotation direction of the impeller 16 from a position corresponding to the suction opening 22 on the pump body 15 to a position corresponding to the discharge opening 24 on the pump cover 9 to form a flow passage groove extending circumferentially from the suction opening 22 to the discharge opening 24. When the impeller 16 rotates in the direction F, fuel is sucked into the flow passage groove from the suction opening 22. While flowing through the flow passage groove from the suction opening 22 to the discharge opening 24, the fuel is pressurized, and the pressurized fuel is delivered to the motor part 2 from the discharge opening 24. Neither of the recesses 21 and 20 are formed in an area extending in the rotation direction of the impeller 16 from a position corresponding to the discharge opening 24 on the pump cover 9 to a position corresponding to the suction opening 22 on the pump body 15, thereby preventing the pressurized fuel from returning to the suction opening 22 side as much as possible. It should be noted that the high-pressure fuel delivered to the motor part 2 is delivered to the outside of the pump from a delivery opening 28.

[0074] The fuel pump according to this embodiment has both the qualitative and quantitative features as stated above and hence exhibits a high pump efficiency. The same pump capacity as that conventionally obtained by supplying a motor current of 2.2 amps can be realized with a motor current of 1.5 amps. 

What is claimed is:
 1. A fuel pump having an impeller rotating in a pump casing, said impeller having an approximately disk-shaped configuration with a group of recesses formed in a region extending along outer peripheries of obverse and reverse sides of said impeller, said recesses being repeatedly arranged at a distance between each other in a circumferential direction with a partition provided between each pair of adjacent recesses, wherein radially inner and outer end portions of said partition are positioned on a same radius, and a radially middle portion of said partition is curved rearward in a direction of rotation of said impeller.
 2. A fuel pump according to claim 1, wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a maximum amount of curvature of said partition is from 0.1 to 1.0 mm.
 3. A fuel pump according to claim 1, wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a curved configuration of a rotation direction forward side of each partition on the obverse and reverse sides is a circular arc with a radius of from 2.3 to 4.3 mm.
 4. A fuel pump according to claim 1, wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a curved configuration of a rotation direction rearward side of each partition on the obverse and reverse sides is a circular arc with a radius of from 3.0 to 5.0 mm.
 5. A fuel pump according to claim 1, wherein said partition is inclined rearward in the direction of rotation as a distance from the obverse and reverse sides increases inward in a direction of thickness.
 6. A fuel pump according to claim 5, wherein said partition is inclined at from 40° to 60° from a middle plane in the direction of thickness.
 7. A fuel pump according to claim 5, wherein said partition continuously extends while defining a gently arcuate surface at a rotation direction forward side of a middle plane in the direction of thickness.
 8. A fuel pump according to claim 1, wherein a thickness of said partition increases as a distance from the obverse and reverse sides increases inward in a direction of thickness.
 9. A fuel pump according to claim 8, wherein the thickness of said partition at a middle plane in the direction of thickness is greater than a thickness thereof at the obverse and reverse sides by from 0.1 to 0.4 mm.
 10. A fuel pump according to claim 1, wherein a radially inner end face of each of said recesses has two arcuate surfaces contacting each other at a middle plane in a direction of thickness.
 11. A fuel pump according to claim 10, wherein a radius of said arcuate surfaces is from 0.7 to 2.2 mm.
 12. A fuel pump according to claim 1, wherein a radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from a middle plane in a direction of thickness.
 13. A fuel pump according to claim 12, wherein the radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness at an open angle of not more than 20°.
 14. A fuel pump according to claim 12, wherein the radially outer end face of each of said recesses has two arcuate surfaces contacting each other at the middle plane in the direction of thickness.
 15. A fuel pump according to claim 14, wherein a radius of said arcuate surfaces is from 0.2 to 1.0 mm.
 16. A fuel pump according to claim 1, wherein said partition is inclined rearward in the direction of rotation as a distance from the obverse and reverse sides increases inward in a direction of thickness and continuously extends while defining a gently arcuate surface at a rotation direction forward side of a middle plane in the direction of thickness; a thickness of said partition increases as a distance from the obverse and reverse sides increases inward in the direction of thickness; a radially inner end face of each of said recesses has two arcuate surfaces contacting each other at the middle plane in the direction of thickness; and a radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness. 